The optical isolator is a key element of modern optical communication networks. Optical isolators allow light to travel in one direction, while blocking light traveling in an opposite direction. The ever-increasing speeds of today's optical networks have placed higher performance demands on optical isolators. Today, network speeds of 40 Gb/s and higher with long haul or ultra-long haul applications are required. Polarization Mode Dispersion (PMD) is a very important criteria which must be minimized in any high-speed, long haul optical communication system.
Dual-stage isolators are known in the art. As is known by those skilled in the art, dual-stage isolators offer the advantage of lower PMD. However, dual-stage isolators of the prior art suffer from the disadvantage of being difficult to manufacture and fabricate. This is because the crystals used to fabricate the dual-stage isolator are typically 22.5° wedges and therefore must be aligned at angles of 45° relative to each other. Precisely aligning optical crystals 45° with respect to each other can be a very difficult task that is time consuming and error prone.